ActiTrexx completes treatment of last patient with novel regulatory T cell therapy against Graft-versus-Host Disease

• Phase Ib/II study with Actileucel, a novel cellular product based on activated regulatory T cells for prevention of Graft-versus-Host Disease (GvHD)
• Follow-up is ongoing to evaluate the safety of Actileucel treatment as well as frequency and severity of potential GvHD
• Actileucel is the first regulatory T cell therapy from an unmatched third-party donor

Mainz, Germany, 20 October 2025 – ActiTrexx GmbH, a clinical-stage company focusing on the activation of regulatory T cells, has completed the treatment of the final patient in its first-in-human study with Actileucel, its novel allogeneic cell therapy for the prevention and treatment of Graft-versus-Host Disease (GvHD).

Actileucel is generated by activating regulatory T cells (Tregs) isolated from an unmatched, third-party donor via a fast proprietary process with a vein-to-vein time of 24 hours.

Prof. Dr. Andrea Tüttenberg, CEO of ActiTrexx, said: “The completion of patient treatment in our Phase Ib/II study marks an important milestone for our Actileucel program. Our approach, which uses activated regulatory T cells from a 3^rd party donor who does not need to match the patient’s tissue markers, has the potential to control or prevent GvHD, a serious and often life-threatening complication following stem cell transplantation. Follow-up continues and once the full dataset is available, we plan on publishing the results in a peer-reviewed journal. The Nobel Prize in Medicine/Physiology awarded this year highlights the fundamental role of regulatory T cells in immune system control, which underlines the scientific rationale behind our approach.”

Prof. Dr. Martin Bornhäuser, Chief Physician and Director Department of Medicine I, University Hospital Carl Gustav Carus in Dresden, commented: “ActiTrexx’s proprietary method for activating and generating regulatory T cells is unique worldwide, highly innovative and represents a promising approach in the field of cell therapy. The use of regulatory T cells from a second donor to potentially control or prevent GvHD offers a novel strategy for a complication that affects half of all stem cell transplant recipients and has historically high mortality.”

The prospective open, single-arm non-randomized multicentric Phase Ib/II study included ten patients who had recently undergone an allogeneic haematopoietic stem cell transplantation as treatment for haematological malignancies such as acute leukemia.

Patients received a single treatment with Actileucel with a follow-up of six months, which is still ongoing for the last patients. Patients in the study were treated with increasing doses of activated regulatory T cells in three cohorts.

Primary endpoint of the study is the safety and tolerability of Actileucel treatment, while secondary endpoints include an assessment of the frequency and severity of GvHD in treated patients as well as of the feasibility of Actileucel manufacturing. The trial is being conducted at four sites in Germany, the III. Medical Clinic of the University Medical Center Mainz, the University Hospital Carl Gustav Carus in Dresden, the University Medical Centre of Münster, and the Internal Medicine II of the St. Johannes Hospital Dortmund.

“We are happy that the manufacturing process at ActiTrexx and the treatments at the study centers could proceed as planned, and we would like to thank everyone involved. We are confident that the study results will bring us a step closer to preventing GvHD via the specific activation of regulatory T cells,” added Dr. Helmut Jonuleit, CSO and Head of Production for ActiTrexx.
 

About GvHD
GvHD is a life-threatening side effect of allogeneic haematopoietic stem cell transplantation. Donor lymphocytes react against tissue antigens in the recipient and cause severe organ and tissue damage, that often takes a chronic course. GvHD is primarily triggered by the donor’s CD4⁺ T cells, whose activity is controlled by regulatory T cells. About 50% of patients develop the disease with a significantly increased mortality rate within 3 years after transplantation. Once developed, patients suffer from the often life-long symptoms.
 

About Actileucel
Actileucel is a cellular therapeutic agent that contains optimally activated regulatory T cells, the natural guardian cells of our immune system. Regulatory T cells modulate the activity of T cells and prevent unwanted inflammatory reactions. Actileucel suppresses the undesired activation of CD4⁺ T cells in the transplant, prevents the development of GvHD and promotes the development of a healthy immune system in the patient. The cellular therapeutic Actileucel is classified as an Advanced Therapy Medicinal Product (ATMP), produced in an automated process and ready for clinical use in patients within 24 hours.
 

About ActiTrexx
ActiTrexx is a clinical phase biotech company developing a platform of cellular and biologic therapies for overshooting T cell mediated autoimmune and autoinflammatory diseases with high medical unmet need. The first product candidate, Actileucel, is a cell therapy based on regulatory T cells that are activated in a proprietary ultrafast process, and is in clinical Phase Ib/II for the treatment of Graft-versus-Host Disease (GvHD) after blood stem cell transplantation. ActiTrexx GmbH was founded in 2020 as a spin-off from the University Medical Center Mainz and is backed by LBBW Venture Capital GmbH, High-Tech Gründerfonds (HTGF), Investitions- und Strukturbank Rheinland-Pfalz (ISB) and MediVentures GmbH. www.actitrexx.de